Recently, Cathode Ray Tube (CRT) display has been gradually replaced by a Liquid Crystal Display (LCD) or an Organic Light-Emitting diode (OLED) display in televisions, mobile phones, computers or laptop computers due to such advantages as small volume, small weight, low power consumption, vivid colors and vivid images.
Usually, the LCD or OLED display is provided with a TFT array substrate which includes a plurality of pixel units. Each pixel unit corresponds to one TFT which functions as a switching element for controlling a state of the corresponding pixel unit. Generally, the TFT corresponding to each pixel unit is required to have a high switching speed during the use of the LCD and OLED display with a large area and a high resolution, so there is a high demand on the conductivity of electrodes of the TFT.
Currently, each electrode of the TFT is usually made of an elemental metal having well conductivity. However, the elemental metal maybe readily oxidized in a subsequent process, and as a result, its conductivity will be deteriorated.